U.S. Pat. No. 4,351,077 to Hofmann and U.S. Pat. No. 4,642,833 to Stoltz, et al., incorporated herein in their entireties by this reference, disclose automatic, water-interruption-type suction swimming pool cleaners having flexible annular discs. These discs are typically mounted near the inlets of the suction cleaners and designed to contact pool surfaces when in use. By doing so, the discs decrease the tendency of the cleaners to disengage from pool surfaces, particularly when the cleaners are negotiating transition regions between walls and floors.
U.S. Pat. No. 4,193,156 to Chauvier, also incorporated herein in its entirety by this reference, describes (at column 4, lines 5-55) an annular disc having numerous "concertina-like," "circumferentially spaced folds." These folds extend when their associated swimming pool cleaner encounters a transition region, purportedly "keeping the inflow of water into the mouth opening to a minimum." Other existing discs similarly are designed for improved adhesion to surfaces to be cleaned, thereby reducing fluid flow into the mouth of the cleaners.